Washing machine and method of controlling the washing machine

ABSTRACT

A washing machine and a method of controlling the washing machine are provided. In the washing machine and the method of controlling the washing machine, a liquid detergent is automatically supplied into a washing tub, thereby improving user convenience. In addition, in the washing machine and the method of controlling the washing machine, a liquid detergent is supplied into the washing tub by water circulated by a circulation unit. Thus, no liquid detergent remains in a liquid detergent supply path, and the liquid detergent supply path can be prevented from being blocked due to the solidification of a liquid detergent.

TECHNICAL FIELD

The present invention relates to a washing machine and a method ofcontrolling the washing machine, and more particularly, to a washingmachine which can automatically supply a liquid detergent into a washingtub while preventing the liquid detergent from remaining in a liquiddetergent supply path, and a method of controlling the washing machine.

BACKGROUND ART

In general, washing machines remove dust and dirt from clothing byperforming a mechanical operation using water and a detergent. In recentyears, an increasing number of washing machines have been equipped witha drier function for drying wet laundry with the use of a mechanicaloperation and hot wind generated by a heater.

A typical washing machine includes a washing tub, which is rotatablyinstalled in the typical washing machine and can contain water andlaundry therein. The typical washing machine performs a washingoperation on laundry contained in the washing tub by rotating thewashing tub with the aid of a driving unit. The typical washing machinealso includes a water supply unit which supplies water into the washingtub, and a drainage unit which drains water from the washing tub. Adetergent supply unit, which supplies a detergent into the washing tub,is disposed on a water supply path of the water supply unit. Thedetergent supply unit includes a dispenser which is connected to thewater supply path and a detergent box which is installed so as to beable to be inserted into or ejected from the dispenser. Therefore, inorder to supply a powder detergent or a liquid detergent into thewashing tub, the detergent box may be taken out from the dispenser, apowder detergent or a liquid detergent may be injected into thedetergent box, and the detergent box may be put back in the disperser.Then, if the water supply unit begins to operate, the powder detergentor the liquid detergent contained in the detergent box may be suppliedinto the washing tub along with water that flows along the water supplypath of the water supply unit.

Conventionally, however, users are required to put a liquid detergentinto a detergent box whenever necessary for a washing operation, therebycausing inconvenience and reducing the convenience of the use of awashing machine.

DISCLOSURE OF INVENTION Technical Problem

The present invention provides a washing machine which can automaticallysupply a liquid detergent into a washing tub while preventing the liquiddetergent from remaining in a liquid detergent supply path, and a methodof controlling the washing machine.

Technical Solution

According to an aspect of the present invention, there is provided awashing machine including a washing tub which contains laundry and watertherein; a circulation unit which circulates the water in the washingtub; a liquid detergent container which contains a liquid detergent tobe supplied into the washing tub; and a liquid detergent supply unitwhich supplies the liquid detergent into the circulation unit andinjects a mixture of the liquid detergent and the water circulated bythe circulation unit into the washing tub.

According to another aspect of the present invention, there is provideda washing machine including a washing tub which contains water therein;a water supply path along which water is supplied from an external watersource into the washing tub; a liquid detergent container which containsa liquid detergent; a circulation unit which circulates the water in thewashing tub; and a circulation path along which a mixture of the liquiddetergent and the water circulated by the circulation unit is suppliedinto the washing tub.

According to another aspect of the present invention, there is provideda method of controlling a washing machine, the method includingsupplying water into a washing tub; and discharging the water from thewashing tub, mixing the discharged water with a liquid detergent in aliquid detergent container and injected the mixture of the dischargedwater and the liquid detergent into the washing tub.

According to the present invention, it is possible to improve userconvenience by automatically supplying a liquid detergent into a washingtub. In addition, it is possible to prevent a liquid detergent fromremaining in a liquid detergent supply path and prevent the liquiddetergent supply path from being blocked due to the solidification of aliquid detergent by supplying a liquid detergent into a washing tub withthe use of water circulated by a circulation unit.

Moreover, according to the present invention, it is possible to preventa waste of liquid detergent and the deterioration of the performance ofa washing machine by precisely controlling the amount of liquiddetergent supplied into a washing tub.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail preferred embodimentsthereof with reference to the attached drawings in which:

FIG. 1 illustrates a perspective view of a drum-type washing machineaccording to an embodiment of the present invention;

FIG. 2 illustrates a partially exploded perspective view of a main bodyof the drum-type washing machine illustrated in FIG. 1;

FIG. 3 illustrates a cross-sectional view of the drum-type washingmachine illustrated in FIG. 1;

FIG. 4 illustrates a block diagram of the drum-type washing machineillustrated in

FIG. 1;

FIG. 5 illustrates a cross-sectional view of a drum-type washing machineaccording to another embodiment of the present invention; and

FIG. 6 illustrates a block diagram of the drum-type washing machineillustrated in FIG. 5.

MODE FOR THE INVENTION

The present invention will hereinafter be described in detail withreference to the accompanying drawings in which exemplary embodiments ofthe invention are shown.

FIGS. 1 through 4 illustrate diagrams of a drum-type washing machine 100according to an embodiment of the present invention. Referring to FIG.1, the drum-type washing machine 100 includes a main body 102 whichperforms a washing operation on laundry; and a frame 104 which isdisposed on one side of the main body 102 and contains various stuffsnecessary for the use of the main body 102.

A laundry inlet/outlet hole 2 a, through which laundry can be injectedinto or ejected from the main body 102, is formed at the front of themain body 102. A door 2 b is rotatably installed so as to be able toopen or close the laundry inlet/outlet hole 2 a. A plurality of legs 2d, which support the main body 102, are formed at the bottom of the mainbody 102. A drawer-type container 106 is installed so as to be able toslide in and out of the frame 104. The drawer-type container 105 may beejected forward from the frame 104.

The frame 104 may be selectively disposed on the top, the bottom, a leftside, a right side, or a rear side of the main body 102. In theembodiment of FIGS. l through 4, the frame 104 is disposed below themain body 102. A plurality of leg settling units 108 respectivelycorresponding to the legs 2 d are formed on the top of the frame 104.Once the main body 102 is mounted on the frame 104, the laundryinlet/outlet hole 2 a is lifted up by as much as the height of the frame104, and thus a user can easily access the main body 102. Therefore, theframe 104 not only contains various goods but also lifts up the mainbody 102 to the extent that the convenience of the use of the main body102 can be improved.

Referring to FIGS. 2 and 3, the main body 102 includes a case 2 whichforms the exterior of the main body 102, a washing tub 4 which isrotatably installed in the case 2 and contains laundry, a detergent andwater, and a driving unit 6 which drives the washing tub 4.

The washing tub 4 may include a tub 8 which is installed so as to beable to be buffered by a spring 8 a and a damper 8 c and contains waterand a detergent therein; a drum 10 which is rotatably installed in thetub 8, contains laundry and includes a plurality of water holes 10 athrough which water and a detergent contained in the tub 8 can pass; anda lifter 12 which is disposed in the drum 10 and lifts up and dropslaundry during the rotation of the drum 10.

An opening 8 b is formed at the front of the tub 8, and an opening 10 bis formed at the front of the drum 10. The laundry inlet/outlet hole 2 ais formed at the front of the case 2 and faces the openings 8 b and 10b. The door 2 b is rotatably installed at the front of the case 2. Agasket 14 is disposed between the opening 8 b of the tub 8 and thelaundry inlet/outlet hole 2 a. The gasket 14 alleviates shock caused bythe rotation of the drum 10 and prevents a water spill.

Referring to FIGS. 2 and 3, the main body 102 also includes a watersupply unit 16 which is disposed above the tub 8 and supplies water intothe tub 8; and a detergent supply unit 18 which is disposed on a watersupply path of the water supply unit 16 and supplies a detergent intothe tub 8.

The water supply unit 16 includes a plurality of water supply valves 20which are disposed in the case 2 and are connected to an external watersource, and the water supply path which connects the water supply valves20 and the tub 8 and guides water into the tub 8. The water supply pathincludes a plurality of first water supply hoses 22 which connect therespective water valves 20 to the detergent supply unit 18 and a secondwater supply hose 24 which connects the detergent supply unit 18 and thetub 8.

The detergent supply unit 18 is provided with a detergent by a userbefore the operation of the drum-type washing machine 100 and suppliesthe detergent into the tub 8 during the operation of the drum-typewashing machine 100. The detergent supply unit 18 includes a dispenser26 and a detergent box 28 which is installed in the dispenser 26 so asto be able to be inserted into or ejected from the dispenser 26 andincludes a plurality of detergent containers 28 a into which a detergentcan be supplied by the user. The first water supply hoses 22 areconnected to the top of the dispenser 26, and the second water supplyhose 24 is connected to the bottom of the dispenser 26. The dispenser 26has an open front and is connected to a hole 2 c, which is formed at thefront of the case 2. The detergent box 28 is disposed so as to be ableto be inserted into or ejected from the dispenser 26 through the hole 2c of the case 2. Therefore, the dispenser 26 selectively distributeswater supplied thereto through the first water supply hoses 22 among thedetergent containers 28 a and then supplies water mixed with a detergentin the detergent containers 28 a into the tub 8 through the second watersupply hose 24. A powder detergent, a liquid detergent or both may besupplied into the detergent supply unit 18.

Referring to FIGS. 2, 3 and 4, the main body 102 also includes adrainage unit 30, which is disposed below the tub 8 and drains water anda detergent from the tub 8. The drainage unit 30 includes a drain pathwhich guides water in the tub 8 to the outside of the case 2; a drainfilter 32 which is disposed on the drain path and removes foreignmaterials from drain water; and a drain pump 34 which is disposed in thedrain filter 32 and flows water along the drain path. The drain pathincludes a first drain hose 36 which connects a lower portion of the tub8 and the drain filter 32 and a second drain hose 38 which has one endconnected to the drain filter 32 and the other end disposed outside thecase 2.

Referring to FIGS. 3 and 4, the main body 102 also includes acirculation unit 40 which is disposed on one side of the tub 8 andcirculates water in the tub 8. Due to the circulation unit 40, laundryin the drum 10 can be evenly soaked with water within a relatively shorttime. The circulation unit 40 includes a circulation path which connectsboth end portions of the tub 8 at different heights; a circulationfilter 42 which removes foreign materials from water that flows alongthe circulation path; a circulation pump 44 which is disposed in thecirculation filter 42 and circulates water in the tub 8 so as to flowalong the circulation path; and a circulation nozzle 46 which isdisposed on one side of the circulation path, from which water isdischarged, and injects water into the tub 8.

The circulation pump 44 is driven when the tub 8 is filled with acertain amount of water by the water supply unit 16, and forcefullycirculates the water in the tub 8 from one end to the other end of thecirculation path. The circulation nozzle 46 is formed through the top ofthe gasket 14 and thus sprinkles water supplied thereto from thecirculation path on laundry. The circulation nozzle 46 may be optional.The circulation nozzle 46 may be installed directly at the tub 8. Thecirculation path includes a first circulation hose 48 which connects thelower portion of the tub 8 and the circulation filter 42 and a secondcirculation hose 49 which has one end connected to the circulationfilter 42 and the other end connected to the circulation nozzle 46.

Referring to FIGS. 1 and 3, the frame 104 also includes at least oneliquid detergent container 50 which contains at least one type of liquiddetergent to be supplied into the tub 8. The liquid detergent container50 is disposed in the drawer-type container 106. A number of liquiddetergent containers 50 corresponding to the number of types of liquiddetergents used in a washing operation may be provided in the drum-typewashing machine 100. In the embodiment of FIGS. 1 through 4, only oneliquid detergent container 50 is provided in the drum-type washingmachine 100, and only one type of liquid detergent is used in a washingoperation performed by the drum-type washing machine 100. The liquiddetergent container 50 includes an injection hole 52 which is formed onthe top of the liquid detergent container 50 and through which a liquiddetergent is injected into the liquid detergent container 50. A cover 54is formed so as to be able to open and close the injection hole 52. Whenthe drawer-type container 106 is ejected from the dispenser 108, theinjection hole 52 is completely exposed.

Referring to FIGS. 3 and 4, the drum-type washing machine 100 alsoincludes a liquid detergent supply unit 60 which automatically suppliesa liquid detergent contained in the liquid detergent container 50 intothe tub 8. The liquid detergent supply unit 60 automatically supplies anappropriate amount of liquid detergent into the tub 8 according to theamount of laundry in the drum 10. Therefore, the supply of a detergentby the detergent supply unit 18 may not be performed.

Referring to FIGS. 1, 3 and 4, the liquid detergent supply unit 60includes a liquid detergent supply path 62 which connects the liquiddetergent container 50 and the circulation unit 40; and a liquiddetergent supply pump 64 which is disposed on the liquid detergentsupply path 62.

The liquid detergent supply path 62 has a first end connected to theliquid detergent container 50 in the frame 104 and a second endconnected to the circulation path of the circulation unit 40 in the mainbody 102. The second end of the liquid detergent supply path 62 isconnected to the first circulation hose 48, which is less affected bypressure caused by the circulation pump 44 during the operation of thecirculation unit 40. Alternatively, the second end of the liquiddetergent supply path 62 may be connected to the circulation pump 44 orthe circulation nozzle 46.

The liquid detergent supply path 62 passes through the top of the frame104 and the bottom of the main body 102. Therefore, the liquid detergentsupply path 62 may be divided into more than one portion that can beselectively connected to or disconnected from each other, therebyfacilitating the installation of the liquid detergent supply path 62 inthe drum-type washing machine 100. The liquid detergent supply path 62may be formed as a hose having a sufficient length to not interfere withthe ejection of the drawer-type container 106.

The liquid detergent supply pump 64 pumps a liquid detergent out of theliquid detergent container 50, which is disposed below the tub 8, andthus forcefully flows the liquid detergent into the circulation unit 40through the liquid detergent supply path 62. The liquid detergent supplypump 64 is disposed in the frame 104. The liquid detergent supply pump64 may be disposed in the main body 102.

The amount of liquid detergent supplied by the liquid detergent supplyunit 60 is controlled according to the number of revolutions per minuteof the liquid detergent supply pump 64 and the duration of the operationof the liquid detergent supply pump 64. In the embodiment of FIGS. 1through 4, the number of revolutions per minute of the liquid detergentsupply pump 64 is uniformly maintained, and thus, the amount of liquiddetergent supplied by the liquid detergent supply pump 64 is determinedaccording to the duration of the operation of the liquid detergentsupply pump 64. That is, once the amount of liquid detergent to besupplied is set according to the amount of laundry injected into thedrum 10 and a washing course, the liquid detergent supply pump 64 iscontinuously driven for an amount of time corresponding to the setamount of liquid detergent, and thus, the set amount of liquid detergentcan be supplied into the tub 8.

Referring to FIGS. 3 and 4, the liquid detergent supply unit 60 alsoincludes a check valve 66, which is disposed on the liquid detergentsupply path 62 and limits the direction of the flow of a liquiddetergent from the liquid detergent container 50 to the circulation unit40. That is, the check valve 66 prevents water and foreign materials inthe first circulation hose 48 from flowing into the liquid detergentcontainer 50 along the liquid detergent supply path 62 during theoperation of the circulation unit 40. The check valve 66 is disposedbetween the liquid detergent supply pump 64 and the circulation unit 40in order to prevent the operating pressure of the circulation unit 40from affecting the liquid detergent supply pump 64. Thus, it is possibleto reduce damage to the liquid detergent supply pump 64, caused bypressure generated during the operation of the circulation unit 40.

Referring to FIGS. 3 and 4, the liquid detergent supply unit 60 alsoincludes a liquid detergent mixer 68, which is connected to theconnection between the liquid detergent supply path 62 and thecirculation unit 40 and mixes a liquid detergent with water. The liquiddetergent mixer 68 is formed as a cylinder having an empty spacetherein. The liquid detergent mixer 68 is connected to the liquiddetergent supply path 62, and thus, a liquid detergent that flows alongthe liquid detergent supply path 62 can be injected into the liquiddetergent mixer 68. In addition, the liquid detergent mixer 68 isconnected to a middle portion of the first circulation hose 48, andthus, water that flows along the first circulation hose 48 can beinjected into the liquid detergent mixer 68 and mixed with the liquiddetergent injected into the liquid detergent mixer 68. Then, the liquiddetergent mixer 68 supplies a liquid detergent completely dissolved inwater into the drum 10 through the circulation nozzle 46.

As the difference between the height of the liquid detergent mixer 68and the height of the liquid detergent container 50 increases, the pumphead of the liquid detergent supply pump 64 increases. Accordingly, therequired capacity of the liquid detergent supply pump 64 increases, andthe manufacturing cost of the liquid detergent supply pump 64 increases.Therefore, the liquid detergent mixer 68 may be disposed between the tub8 and the liquid detergent container 8 so as to be as close as possibleto the liquid detergent container 50.

The operation of the drum-type washing machine 100 will hereinafter bedescribed in detail. Assume that the detergent supply unit 18 suppliesno detergent, and that the liquid detergent supply unit 60 supplies aliquid detergent instead.

Laundry is injected into the drum 10 through the laundry inlet/outlethole 2 a of the main body 102, and the door 2 b is closed so that thelaundry inlet/outlet hole 2 a can be sealed. Then, the main body 102 isdriven. The main body 102 detects the amount of laundry injected intothe drum 10, and sets a feed-water level, an amount of detergent to besupplied, and a washing time.

Thereafter, the water supply unit 16 is driven and thus supplies waterinto the tub 8 until reaching the set feed-water level. Morespecifically, the water supply valve 20 of the water supply unit 16 isopened so that water can be injected from an external water source intothe drum-type washing machine 100 through the water supply valve 20 andthen supplied into the tub 8 through the first water supply hose 22, thedetergent supply unit 18, and the second water supply hose 24.Thereafter, the liquid detergent supply unit 60 supplies the set amountof detergent into the tub 8. More specifically, when the liquiddetergent supply pump 64 of the liquid detergent supply unit 60 isdriven, the liquid detergent supply pump 64 pumps a liquid detergent outof the liquid detergent container 50 so that the liquid detergent can beinjected into the liquid detergent mixer 68 along the liquid detergentsupply path 62.

Thereafter, the circulation unit 40 is driven so that the water injectedinto the tub 8 can circulate, and that the liquid detergent in theliquid detergent mixer 68 can be supplied into the tub 8.

Thereafter, the driving unit 6 is driven so that the drum 10 can rotatefor a predefined amount of time. Accordingly, a washing operation isperformed while repeatedly lifting up and dropping the laundry with theuse of the rotation of the drum 10 and the lifter 12.

Once the washing operation is complete, the operation of the drivingunit 6 is terminated, and the drainage unit 30 is driven and thus drainswater from the tub 8. Thereafter, the water supply unit 16 is driven andthus supplies water into the tub 8 until reaching the set feed-waterlevel. Thereafter, the driving unit 6 is driven and thus rotates thedrum 10 again, thereby performing a rinsing operation.

Once the rinsing operation is complete, the operation of the drivingunit 6 is terminated, and the drainage unit 30 is driven and thus drainswater from the tub 8. Thereafter, if the tub 8 is completely drained,the driving unit 6 is driven and thus rotates the drum 10 at high speed,and then, the operation of the drum-type washing machine 100 isterminated. When the drum 10 is rotated at high speed, water drains fromthe laundry, and water collected in the tub 8 is discharged by thedrainage unit 30.

The supply of a liquid detergent as performed in the drum-type washingmachine 100 will hereinafter be described in detail with reference toFIG. 4. Referring to FIG. 4, solid-line arrows indicate water flowcaused by the circulation unit 40, and dotted-line arrows indicate waterflow caused by the liquid detergent supply unit 60.

Referring to FIG. 4, the liquid detergent supply pump 64 is driven andthus pumps a liquid detergent out of the liquid detergent container 50.Then, the liquid detergent flows along the liquid detergent supply path,and thus, a predefined amount of liquid detergent is supplied into theliquid detergent mixer 68.

The amount of liquid detergent supplied by the liquid detergent supplypump 64 may be determined indirectly based on the duration of theoperation of the liquid detergent supply pump 64. Therefore, if theduration of the operation of the liquid detergent supply pump 64 is morethan a predefined amount of time, the operation of the liquid detergentsupply pump 64 is terminated. The predefined amount of time may be setaccording to the amount of laundry, a washing course and the type ofliquid detergent used in the drum-type washing machine 100.Alternatively, the amount of liquid detergent supplied by the liquiddetergent supply pump 64 may be measured by installing a water levelsensor or a weight sensor in the liquid detergent container 50. If anappropriate amount of liquid detergent is injected into the liquiddetergent mixer 68, it is determined whether a current water level inthe tub 8 is appropriate for a circulation operation. If the currentwater level in the tub 8 is appropriate for a circulation operation, thecirculation unit 40 may be driven.

When the circulation unit 40 is driven, the water in the tub 8 isinjected into the circulation pump 44 through the first circulation hose48. Then, the water injected into the circulation pump 44 is injectedinto the liquid detergent mixer 68 through the first circulation hose48. The liquid detergent contained in the liquid detergent mixer 68dissolves in and mixes with the water injected into the liquid detergentmixer 68, and then the mixture is injected into the circulation pump 44.The mixture flows to the circulation nozzle 46 along the secondcirculation hose 49 and then is injected into the drum 10.

In the embodiment of FIGS. 1 through 4, the liquid detergent supply unit60 and the circulation unit 40 supply a liquid detergent mixed withwater into the tub 8 and thus prevent laundry in the drum 10 fromdirectly contacting a liquid detergent. Therefore, it is possible toprevent laundry from being damaged or decolorized due to directlycontacting a liquid detergent. In addition, in the embodiment of FIGS. 1through 4, a liquid detergent is supplied into the tub 8 along withwater circulated by the circulation unit 40, and thus, no liquiddetergent remains in the liquid detergent supply unit 50 and thecirculation unit 40. Therefore, since a liquid detergent only remains inthe tub 8, it is possible to supply an appropriate amount of liquiddetergent into the tub 8, to prevent the liquid detergent supply path 62of the liquid detergent supply unit 60 and the circulation path of thecirculation unit 40 from being blocked due to the solidification of aliquid detergent remained therein.

FIG. 5 illustrates a cross-sectional view of a drum-type washing machine200 according to another embodiment of the present invention, and FIG. 6illustrates a block diagram of the drum-type washing machine 200. InFIGS. 1 through 6, like reference numerals indicate like elements, andthus detailed descriptions thereof will be skipped. The drum-typewashing machine 200 will hereinafter be described, mainly focusing onthe differences with the drum-type washing machine 100.

Referring to FIGS. 5 and 6, the drum-type washing machine 200 isdifferent from the drum-type washing machine 100 in that the drum-typewashing machine 200 does not include a frame, that a circulation unit240 and a drainage unit 30 share some elements, and that a liquiddetergent container 250 is disposed in a case 2 of the drum-type washingmachine 200. Referring to FIG. 6, solid-line arrows indicate water flowcaused by the circulation unit 240, and dotted-line arrows indicatewater flow caused by a liquid detergent supply unit 260.

The drainage unit 30, like the drainage unit 30 of the drum-type washingmachine 100, includes a drain pump 34, a drain filter 32, a first drainhose 36, and a second drain hose 38. The circulation unit 240, like thecirculation unit 40 of the drum-type washing machine 100, includes acirculation pump 44, a second circulation hose 49, and a circulationnozzle 46. However, the circulation unit 240, unlike the circulationunit 40 of the drum-type washing machine 100, uses the drain filter andthe first drain hose 36 of the drainage unit 30 as a circulation filterand a first circulation hose. That is, the drain filter 32 performs thefunctions of the circulation filter 42 of the circulation unit 40 of thedrum-type washing machine 100, and the first drain hose 36 performs thefunctions of the first circulation hose 48 of the circulation unit 40 ofthe drum-type washing machine 100. By sharing the drain filter 32 andthe first drain hose 36 between the drainage unit 30 and the circulationunit 240, it is possible to simplify the structure of the drum-typewashing machine 200, to reduce the number of elements of the drum-typewashing machine 200 and thus to reduce the manufacturing cost of thedrum-type washing machine 200.

At least one liquid detergent container 250 may be disposed in the case2 of the drum-type washing machine 200. In the embodiment of FIGS. 5 and6, only one liquid detergent container 250 is disposed in the case 2.The liquid detergent supply unit 260 includes a liquid detergent mixer268 which is disposed at a middle portion of the first drain hose 36, aliquid detergent supply path 62 which is connected to the liquiddetergent mixer 268 and the liquid detergent container 250, and a liquiddetergent supply pump 64 which is disposed on the liquid detergentsupply path 62.

An appropriate amount of liquid detergent may be supplied into theliquid detergent mixer 268 by the liquid detergent supply unit 260, andthen, the liquid detergent contained in the liquid detergent mixer 268may be supplied into the drum 10 by the circulation unit 240. Since aliquid detergent is supplied into the tub 8 along with water circulatedby the circulation unit 240, no liquid detergent remains in the liquiddetergent mixer 268. Even if a liquid detergent is not completely washedout from the liquid detergent mixer 268 by the water circulated by thecirculation unit 240 and thus remains in the liquid detergent mixer 268,the liquid detergent remained in the liquid detergent mixer 268 may bedischarged during a drainage operation performed by the drainage unit30.

The present invention is not restricted to the embodiments set forthherein. In addition, the present invention is not restricted to adrum-type washing machine. That is, the present invention can be appliedto a water stream-type washing machine.

In the present invention, if a liquid detergent container is disposedabove a tub, a liquid detergent supply pump may be optional because aliquid detergent can be automatically supplied into the tub due togravity. In addition, in the present invention, a liquid detergent mixermay not be provided. Then, a liquid detergent may be directly suppliedinto a circulation path of a circulation unit.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A washing machine comprising: a washing tub which contains laundryand water therein; a circulation unit which circulates the water in thewashing tub; a liquid detergent container which contains a liquiddetergent therein; and a liquid detergent supply unit which supplies theliquid detergent into the circulation unit and injects a mixture of theliquid detergent and the water circulated by the circulation unit intothe washing tub.
 2. The washing machine of claim 1, wherein thecirculation unit comprises a circulation path which connects first andsecond portions of the washing tub and a circulation pump which isdisposed on the circulation path, and the liquid detergent supply unitis connected to at least one of the circulation path and the circulationpump.
 3. The washing machine of claim 1, wherein the liquid detergentsupply unit comprises a liquid detergent supply path which connects theliquid detergent container and the circulation unit and a liquiddetergent supply pump which is disposed on the liquid detergent supplypath.
 4. The washing machine of claim 3, wherein the liquid detergentsupply unit further comprises a check valve which is disposed on theliquid detergent supply path and prevents the liquid detergent fromflowing backward from the circulation unit to the liquid detergentcontainer.
 5. The washing machine of claim 4, wherein the check valve isdisposed between the liquid detergent supply pump and the circulationunit.
 6. The washing machine of claim 3, wherein the liquid detergentsupply unit further comprises a liquid detergent mixer which isconnected to a connection between the liquid detergent supply path andthe circulation unit and mixes the liquid detergent with the watercirculated by the circulation unit.
 7. The washing machine of claim 1,further comprising: a drainage unit which is connected to thecirculation unit and discharges water remained water in the liquiddetergent mixer.
 8. The washing machine of claim 7, wherein the drainageunit comprises a drain path which is connected to the circulation unitand a drain pump which is disposed on the drain path.
 9. The washingmachine of claim 8, wherein the circulation unit comprises a circulationpath which connects first and second portions of the washing tub and acirculation pump which is disposed on the circulation path, and thecirculation pump and the drain pump are formed in one body.
 10. Thewashing machine of claim 1, further comprising: a main body whichincludes the washing tub and the circulation unit; and a frame which isdisposed on one side of the main body and includes the liquid detergentcontainer.
 11. The washing machine of claim 10, wherein the frame isdisposed below the main body and supports the main body.
 12. A washingmachine comprising: a washing tub which contains water therein; a watersupply path along which water is supplied from an external water sourceinto the washing tub; a liquid detergent container which contains aliquid detergent therein; a circulation unit which circulates the waterin the washing tub; and a circulation path along which a mixture of theliquid detergent and the water circulated by the circulation unit issupplied into the washing tub.
 13. The washing machine of claim 12,further comprising a liquid detergent mixer which is disposed on thecirculation path and mixes the liquid detergent with the watercirculated by the circulation unit.
 14. The washing machine of claim 13,wherein, after the supply of the liquid detergent into the liquiddetergent mixer is complete, the water circulated by the circulationunit is injected into the liquid detergent mixer.
 15. A method ofcontrolling a washing machine, the method comprising: supplying waterinto a washing tub; and discharging the water from the washing tub,mixing the discharged water with a liquid detergent in a liquiddetergent container and injected the mixture of the discharged water andthe liquid detergent into the washing tub.
 16. The method of claim 15,wherein the injecting comprises supplying the liquid detergent from theliquid detergent container into a liquid detergent mixer; anddischarging the water in the washing tub into the liquid detergentmixer, mixing the discharged water with the liquid detergent, andinjecting the mixture of the discharged water and the liquid detergentinto the washing tub.
 17. The method of claim 16, wherein the injectingfurther comprises, after the supply of the liquid detergent into theliquid detergent mixer is complete, discharging the water from thewashing tub into the liquid detergent mixer.
 18. The method of claim 16,wherein the injecting further comprises, if the water supplied into thewashing tub reaches a predefined water level, supplying the liquiddetergent into the liquid detergent mixer.